The invention relates to xcex1-amino ketones which can be converted photochemically into amidine derivatives, to a process for their preparation and to a process for the photochemical preparation of the amidine derivatives. Further subjects of the invention are base-polymerizable or crosslinkable compositions comprising these xcex1-amino ketones, a method of implementing photochemically induced, base-catalysed reactions, and the use of the xcex1-amino ketones as photoinitiators for base-catalysed reactions.
The photolytic cleavage of specific xcex1-amino ketones into free radicals and the photopolymerization of olefinically unsaturated monomers or oligomers which this initiates have long been known and are described, for example, in U.S. Pat. No. 5,077,402.
In addition to free-radically polymerizable oligomers or monomers, base-catalysable systems have been disclosed in particular for photolithographic processes. These systems require a photoinitiator which on exposure to light releases a base. D. R. MacKean et al., Polym. Mater. Sci. Eng. (1992), 66, 237-238 report, for example, on the photostructuring of polyimide using specific carbamates as photoinitiators.
It has now surprisingly been found that certain xcex1-amino ketones which comprise a structural unit of the formula (I) 
release an amidine group on exposure to visible or UV light. This amidine group is sufficiently basic to initiate a large number of base-catalysable reactions, especially polymerization reactions. The compounds are of high sensitivity and through the choice of the substituent R1 the absorption spectrum can be varied within a wide range.
The compounds make it possible to prepare so-called one-pot systems with base-catalysable oligomers or monomers having an extremely long storage life. A polymerization reaction, for example, is initiated only after exposure to light. The systems can be formulated with little or no solvent, since the compounds can be dissolved in the monomers or oligomers without being affected. The active catalyst is formed only after exposure to light. These systems can be employed for numerous purposes, such as for finishes, coatings, moulding compounds or photolithographic reproductions.
The invention provides organic compounds having a molecular weight of less than 1000, comprising at least one structural unit of the formula (I) 
in which R1 is an aromatic or heteroaromatic radical capable of absorbing light in the wavelength range from 200 to 650 nm and in doing so brings about cleavage of the adjacent carbon-nitrogen bond. The structural unit of the formula (I) features a divalent and monovalent nitrogen atom and a divalent and monovalent carbon atom, the nitrogen atoms being in xcex2 position relative to one another.
By aromatic or heteroaromatic radicals R1 are meant those which conform to the Hxc3xcckel 4n+2 rule.
The absorption maximum can be varied within a wide range through the choice of the aromatic or heteroaromatic radical R1, and so the photosensitivity of the compounds can be shifted from the UV into the daylight region.
Preference is given to organic compounds in which the structural unit of the formula (I) comprises compounds of the formula (II) 
in which
R1 is an aromatic or heteroaromatic radical which is capable of absorbing light in the wavelength range from 200 to 650 nm and in doing so brings about cleavage of the adjacent carbon-nitrogen bond;
R2 and R3 independently of one another are hydrogen, C1-C18alkyl, C3-C18alkenyl, C3-C18alkynyl or phenyl and, if R2 is hydrogen or C1-C18alkyl, R3 is additionally a group xe2x80x94COxe2x80x94R14 in which R14 is C1-C18alkyl or phenyl; or R1 and R3, together with the carbonyl group and the C atom to which R3 is attached, form a benzocyclopentanone radical;
R5 is C1-C18alkyl or NR15R16;
R4, R6, R7, R15 and R16 independently of one another are hydrogen or C1-C18alkyl; or
R4 and R6 together form a C2-C12alkylene bridge or
R5 and R7 together, independently of R4 and R6, form a C2-C12alkylene bridge or, if R5 is NR15R16, R16 and R7 together form a C2-C12alkylene bridge.
Alkyl in the various radicals having up to 18 carbon atoms is a branched or unbranched radical such as methyl, ethyl, propyl, isopropyl, n-butyl, sec-butyl, isobutyl, tert-butyl, 2-ethylbutyl, n-pentyl, isopentyl, 1-methylpentyl, 1,3-dimethylbutyl, n-hexyl, 1-methylhexyl, n-heptyl, isoheptyl, 1,1,3,3-tetramethylbutyl, 1-methylheptyl, 3-methylheptyl, n-octyl, 2-ethylhexyl, 1,1,3-trimethylhexyl, 1,1,3,3-tetramethylpentyl, nonyl, decyl, undecyl, 1-methylundecyl, dodecyl, 1,1,3,3,5,5-hexamethylhexyl, tridecyl, tetradecyl, pentadecyl, hexadecyl, heptadecyl, octadecyl. Preference is given to alkyl having 1 to 12, especially 1 to 6 carbon atoms.
Alkenyl having 3 to 18 carbon atoms is a branched or unbranched radical such as propenyl, 2-butenyl, 3-butenyl, isobutenyl, n-2,4-pentadienyl, 3-methyl-2-butenyl, n-2-octenyl, n-2-dodecenyl, iso-dodecenyl, oleyl, n-2-octadecenyl or n-4-octadecenyl. Preference is given to alkenyl having 3 to 12, especially 3 to 6 carbon atoms.
Alkynyl having 3 to 18 carbon atoms is a branched or unbranched radical such as propynyl (xe2x80x94CH2xe2x80x94CHxe2x89xa1CH), 2-butynyl, 3-butynyl, n-2-octynyl, or n-2-octadecynyl. Preference is given to alkynyl having 3 to 12, especially 3 to 6 carbon atoms.
The C2-C2alkylene bridge is ethylene, propylene, butylene, pentylene, hexylene, heptylene, octylene, nonylene, decylene, undecylene or dodecylene.
R1 is preferably an aromatic radical which is unsubstituted or substituted one or more times by C1-C18alkyl, C3-C18alkenyl, C3-C18alkynyl, C1-C18haloalkyl, NO2, NR8R9, N3, OH, CN, OR10, SR10, C(O)R11, C(O)OR12 or halogen and is selected from the group consisting of phenyl, naphthyl, phenanthryl, anthracyl, pyrenyl, 5,6,7,8-tetrahydro-2-naphthyl, 5,6,7,8-tetrahydro-1-naphthyl, thienyl, benzo[b]thienyl, naphtho[2,3-b]thienyl, thiathrenyl, dibenzofuryl, chromenyl, xanthenyl, thioxanthyl, phenoxathiinyl, pyrrolyl, imidazolyl, pyrazolyl, pyrazinyl, pyrimidinyl, pyridazinyl, indolizinyl, isoindolyl, indolyl, indazolyl, purinyl, quinolizinyl, isoquinolyl, quinolyl, phthalazinyl, naphthyridinyl, quinoxalinyl, quinazolinyl, cinnolinyl, pteridinyl, carbazolyl, xcex2-carbolinyl, phenanthridinyl, acridinyl, perimidinyl, phenanthrolinyl, phenazinyl, isothiazolyl, phenothiazinyl, isoxazolyl, furazanyl, terphenyl, stilbenyl, fluorenyl or phenoxazinyl, or R1 is a radial of the formulae A, B or C 
in which
R8, R9, R10, R11 and R12 are hydrogen or C1-C18alkyl;
R13 is C1-C18alkyl, C2-C18alkenyl, C2-C18alkynyl, C1-C18haloalkyl, NO2, NR8R9, OH, CN, OR10, SR10, C(O)R11, C(O)OR12 or halogen; and n is 0 or a number 1, 2 or 3.
Examples of C1-C18alkyl, C3-C18alkenyl and C3-C18alkynyl have already been indicated above.
Halogen is fluorine, chlorine, bromine or iodine.
Examples of C1-C18haloalkyl are fully or partly halogenated C1-C18alkyl. The halogen (halo) here is F, Cl, Br, or I. Examples are the positional isomers of mono- to decafluoropentyl, mono- to octafluorobutyl, mono- to hexafluoropropyl, mono- to tetrafluoroethyl and mono- and difluoromethyl and also the corresponding chloro, bromo and iodo compounds. Preference is given to the perfluorinated alkyl radicals. Examples of these are perfluoropentyl, perfluorobutyl, perfluoropropyl, perfluoroethyl and, in particular, trifluoromethyl.
Examples of the NR8R9 amino group are the respective monoalkyl or dialkylamino groups such as methylamino, ethylamino, propylamino, butylamino, pentylamino, hexylamino, octadecylamino, dimethylamino, diethylamino, dipropylamino, diisopropylamino, di-n-butylamino, di-isobutylamino, dipentylamino, dihexylamino or dioctadecylamino. Further dialkylamino groups are those in which the two radicals independently of one another are branched or unbranched, for example methylethylamino, methyl-n-propylamino, methylisopropylamino, methyl-n-butylamino, methylisobutylamino, ethylisopropylamino, ethyl-n-butylamino, ethylisobutylamino, ethyl-tert-butylamino, isopropyl-n-butylamino or isopropylisobutylamino.
The alkoxy group OR10 having up to 18 carbon atoms is a branched or unbranched radical such as methoxy, ethoxy, propoxy, isopropoxy, n-butoxy, isobutoxy, pentoxy, isopentoxy, hexoxy, heptoxy, octoxy, decyloxy, tetradecyloxy, hexadecyloxy or octadecyloxy. Preference is given to alkoxy having 1 to 12, especially 1 to 8, for example 1 to 6 carbon atoms.
Examples of the thioalkyl group SR10 are thiomethyl, thioethyl, thiopropyl, thiobutyl, thiopentyl, thiohexyl, thioheptyl, thiooctyl or thiooctadecyl, it being possible for the alkyl radicals to be linear or branched.
Examples of the radical R1 are phenyl, naphthyl, phenanthryl, anthracyl, pyrenyl, 5,6,7,8-tetrahydro-2-naphthyl, 5,6,7,8-tetrahydro-1-naphthyl, thienyl, benzo[b]thienyl, naphtho[2,3-b]thienyl, thiathrenyl, dibenzofuryl, chromenyl, xanthenyl, phenoxathiinyl, pyrrolyl, imidazolyl, pyrazolyl, pyrazinyl, pyrimidinyl, pyridazinyl, indolizinyl, isoindolyl, indolyl, indazolyl, purinyl, quinolizinyl, isoquinolyl, quinolyl, phthalazinyl, naphthyridinyl, quinoxalinyl, quinazolinyl, cinnolinyl, pteridinyl, carbazolyl, xcex2-carbolinyl, phenanthridinyl, acridinyl, perimidinyl, phenanthrolinyl, phenazinyl, isothiazolyl, phenothiazinyl, isoxazolyl, furazanyl, biphenyl, stilbenyl, terphenyl, fluorenyl, phenoxazinyl, methoxyphenyl, 2,4-dimethoxyphenyl, 2,4,6-trimethoxyphenyl, bromophenyl, tolyl, xylyl, mesityl, nitrophenyl, dimethylaminophenyl, diethylaminophenyl, aminophenyl, diaminophenyl, 1-naphthyl, 2-naphthyl, 1-phenylamino-4-naphthyl, 1-methylnaphthyl, 2-methylnaphthyl, 1-methoxy-2-naphthyl, 2-methoxy-1-naphthyl, 1-dimethylamino-2-naphthyl, 1,2-dimethyl-4-naphthyl, 1,2-dimethyl-6-naphthyl, 1,2-dimethyl-7-naphthyl, 1,3-dimethyl-6-naphthyl, 1,4-dimethyl-6-naphthyl, 1,5-dimethyl-2-naphthyl, 1,6-dimethyl-2-naphthyl, 1-hydroxy-2-naphthyl, 2-hydroxy-1-naphthyl, 1,4-dihydroxy-2-naphthyl, 7-phenanthryl, 1-anthryl, 2-anthryl, 9-anthryl, 3-benzo[b]thienyl, 5-benzo[b]thienyl, 2-benzo[b]thienyl, 4-dibenzofuryl, 4,7-dibenzofuryl, 4-methyl-7-dibenzofuryl, 2-xanthenyl, 8-methyl-2-xanthenyl, 3-xanthenyl, 2-phenoxathiinyl, 2,7-phenoxathiinyl, 2-pyrrolyl, 3-pyrrolyl, 5-methyl-3-pyrrolyl, 2-imidazolyl, 4-imidazolyl, 5-imidazolyl, 2-methyl-4-imidazolyl, 2-ethyl-4-imidazolyl, 2-ethyl-5-imidazolyl, 3-pyrazolyl, 1-methyl-3-pyrazolyl, 1-propyl-4-pyrazolyl, 2-pyrazinyl, 5,6-dimethyl-2-pyrazinyl, 2-indolizinyl, 2-methyl-3-isdndoly 2-methyl-1-isoindolyl, 1-methyl-2-indolyl, 1-methyl-3-indolyl, 1,5-dimethyl-2-indolyl, 1-3-indazolyl, 2,7-dimethyl-8-purinyl, 2-methoxy-7-methyl-8-purinyl, 2-quinolizinyl, 3-isoquinolyl, 6-isoquinolyl, 7-isoquinolyl, isoquinolyl, 3-methoxy-6-isoquinolyl, 2-quinolyl, 6-quinolyl, 7-quinolyl, 2-methoxy-3-quinolyl, 2-methoxy-6-quinolyl, 6-phthalazinyl, 7-phthalazinyl, 1-methoxy-6-phthalazinyl, 1,4-dimethoxy-6-phthalazinyl, 1,8naphthyridin-2-yl, 2quinoxalinyl, 6-quinoxalinyl, 2,3-dimethyl-6-quinoxalinyl, 2,3-dimethoxy-6-quinoxalinyl, 2-quinazolinyl, 7-quinazolinyl, 2-dimethylamino-6-quinazolinyl, 3-cinnolinyl, 6-cinnolinyl, 7-cinnolinyl, 3-methoxy-7-cinnolinyl, 2-pteridinyl, 6-pteridinyl, 7-pteridinyl, 6,7-dimethoxy-2-pteridinyl, 2-carbazolyl, 3-carbazolyl, 9-methyl-2-carbazolyl, 9-methyl-3-carbazolyl, xcex2-carbolin-3-yl, 1-methyl-xcex2-carbolin-3-yl, 1-methyl-xcex2-carbolin-6-yl, 3-phenanthridinyl, 2-acridinyl, 3-acridinyl, 2-perimidinyl, 1-methyl-5-perimidinyl, 5-phenanthrolinyl, 6-phenanthrolinyl, 1-phenazinyl, 2-phenazinyl, 3-isothiazolyl, 4-isothiazolyl, 5isothiazolyl, 2-phenothiazinyl, 3-phenothiazinyl, 10-methyl-3-phenothiazinyl, 3-isoxazolyl, 4-isoxazolyl, 5-isoxazolyl, 4-methyl-3-furazanyl, 2-phenoxazinyl or 10-methyl-2-phenoxazinyl.
Radicals substituted one or more times are, for example, substituted 1 to 5 times, 1 to 4 times or 3 times, 2 times or once.
Where R1 and R3, together with the carbonyl group and the C atom to which R3 is attached, form a benzocyclopentanone radical, this means structures as follows 
With particular preference R1 is phenyl, naphthyl, pyrenyl, thioxanthyl or phenothiazinyl each of which is unsubstituted or substituted one or more times by C1-C18alkyl, C1-C18haloalkyl, NR8R9, CN, NO2, N3, SR10 or OR10, or R1 is a radical of the formulae A, B or C 
in which n is 0 and the radicals R8, R9, R10 and R13 are as defined above.
Further particularly preferred compounds are those in which R1 is phenyl, naphthyl, anthracyl, thioxanthyl, dibenzofuranyl or pyrenyl, the radicals phenyl, naphthyl, anthracyl, thioxanthyl and pyrenyl being unsubstituted or being substituted one or more times by CN, NR8R9, NO2, halogen, N3, CF3, SR10 or OR10, or R1 is a radical of the formulae A, B, or C. 
in which n is 0 and the radicals R8, R9, R10 and R13 are as defined above. With very particular preference R1 is phenyl, 4-aminophenyl, 4-methylthiophenyl, 4-trifluoromethylphenyl, 4-nitrophenyl, 2,4,6-trimethoxyphenyl, 2,4-dimethoxyphenyl, naphthyl, anthracyl or pyrenyl or a radical of the formula A or B 
R2 and R3 independently of one another are preferably hydrogen or C1-C6alkyl. It is likewise preferred for R4 and R6 together to be a C2-C6alkylene bridge.
Preferably, R5 and R7 are a C2-C6alkylene bridge or, if R5 is NR15R16 and R7 together are a C2-C6alkylene bridge.
R7 is preferably a C2-C6alkylene bridge together with R5 or R7 is C1-C18alkyl which is branched in the xcex1-position of the N-atom.
A particularly preferred group of compounds of the formula (II) are those in which R1 is phenyl, naphthyl, anthracyl, thioxanthyl, dibenzofuranyl or pyrenyl, the phenyl radical being unsubstituted or being substituted one or more times by CN, NR8R9, NO2, N3, halogen, CF3, SR10 or OR10, or R1 is a radical of the formulae A, B or C 
n is 0 and the radicals R8, R9, R10 and R13 are hydrogen or C1-C14alkyl;
R2 and R3 are hydrogen or C1-C6alkyl; or R1 and R3, together with the carbonyl group and the C atom to which R3 is attached, form a benzocyclopentanone radical;
R4, R6 and R7 independently of one another are hydrogen or C1-C6alkyl;
R5 is C1-C6alkyl or NR15R16, where R15 and R16 are hydrogen or C1-C6alkyl; or
R4 and R6 together form a C2-C6alkylene bridge; or, independently of R4 and R6,
R5 and R7 together form a C2-C6alkylene bridge or, if R5 is NR15R16, R16 and R7 together form a C2-C6alkylene bridge.
The invention additionally provides a process for preparing compounds having the structural unit of the formula (I), which comprises reacting a compound comprising a structural unit of the formula (III) 
with a compound comprising a structural unit of the formula (IV) 
in which R1 is as defined above, including the preferred meanings, and Halogen is F, Cl, Br or I, preferably Br.
Preference is given to a process for preparing compounds of the formula (II) which comprises reacting a compound of the formula (V) 
with a compound of the formula (VI) 
in which R1, R2, R3, R4, R5, R6 and R7 are as defined above, including the preferred meanings, and Halogen is F, Cl, Br or I.
The reaction can be carried out in a conventional manner. It is advantageous to use a solvent or solvent mixture, for example hydrocarbons (benzene, toluene, xylene), halogenated hydrocarbons (methylene chloride, chloroform, carbon tetrachloride, chlorobenzene), alkanols (methanol, ethanol, ethylene glycol monomethyl ether) and ethers (diethyl ether, dibutyl ether, ethylene glycol dimethyl ether) or mixtures thereof.
The reaction can be carried out within a temperature range from xe2x88x9210xc2x0 C. to +100xc2x0 C. It is preferably carried out at from 10xc2x0 C. to 50xc2x0 C.
The invention likewise provides a process for preparing a compound of the formula (VII) 
which comprises exposing a compound of the formula (II) 
to light having a wavelength from 200 nm to 650 nm. The reaction is advantageously carried out in a solvent or solvent mixture. The concentration of the compounds of the formula (II) is advantageously adjusted so that virtually all of the light is absorbed in the reaction vessel.
The reaction solution is preferably stirred and, if desired, cooled in the course of the exposure.
Suitable solvents have been listed above.
The invention additionally provides a composition comprising
A) at least one compound having a structural unit of the formula (I) and
B) at least one organic compound capable of a base-catalysed addition or substitution reaction.
Preference is given to compositions comprising as component A) organic components in which the structural unit of the formula (I) comprises compounds of the formula (II) 
in which the radicals R1, R2, R3, R4, R5, R6 and R7 are as defined above, including their preferred meanings.
The base-catalysed addition or substitution reaction can be carried out with low molecular mass compounds (monomers), with oligomers, with polymeric compounds or with a mixture of these compounds. Examples of reactions which can be carried out both with monomers and with oligomers/polymers using the novel photoinitiators are the Knoevenagel reaction or the Michael addition reaction.
Of particular importance are compositions in which component B) is an anionically polymerizable or crosslinkable organic material. The organic material can be in the form of mono- or polyfunctional monomers, oligomers or polymers.
Particularly preferred oligomeric/polymeric systems are binders or coating systems as are customary in the coatings industry.
Examples of such base-catalysable binders or coating systems are:
a) Acrylate copolymers having alkoxysilane or alkoxysiloxane side groups, for example the polymers described in U.S. Pat. Nos. 4,772,672 or 4,444,974;
b) Twocomponent systems comprising hydroxyl-containing polyacrylates, polyesters and/or polyethers and aliphatic or aromatic polyisocyanates;
c) Two-component systems comprising functional polyacrylates and a polyepoxide, where the polyacrylate contains carboxyl or anhydride groups;
d) Two-component systems comprising fluorine-modified or silicone-modified hydroxyl-containing polyacrylates, polyesters and/or polyethers and aliphatic or aromatic polyisocyanates;
e) Two-component systems comprising (poly)ketimines and aliphatic or aromatic polyisocyanates;
f) Two-component systems comprising (poly)ketimines and unsaturated acrylate resins or acetoacetate resins or methyl xcex1-acrylamidomethylglycolate;
g) Two-component systems comprising polyamines and polyacrylates containing anhydride groups;
h) Two-component systems comprising (poly)oxazolidines and polyacrylates containing anhydride groups, or unsaturated acrylate resins or polyisocyanates;
i) Two-component systems comprising epoxy-containing polyacrylates and carboxyl-containing polyacrylates;
l) Polymers based on allyl glycidyl ether;
m) Two-component systems comprising a (poly)alcohol and a (poly)isocyanate;
n) Two-component systems comprising an xcex1,xcex2-ethylenically unsaturated carbonyl compound and a polymer which contains activated CH2 groups, it being possible for the activated CH2 groups to be present either in the main chain or in the side chain or in both, as is described, for example, in EP-B-0 161 697 for (poly)malonate groups. Other compounds having activated CH2 groups are (poly)acetoacetates and (poly)cyanoacetates.
Among these base-catalysable binders particular preference is given to the following:
b) Two-component systems comprising hydroxyl-containing polyacrylates, polyesters and/or polyethers and aliphatic or aromatic polyisocyanates;
c) Two-component systems comprising functional polyacrylates and a polyepoxide, where the polyacrylate contains carboxyl or anhydride groups;
i) Two-component systems comprising epoxy-containing polyacrylates and carboxyl-containing polyacrylates;
m) two-component systems comprising a (poly)alcohol and a (poly)isocyanate, and
n) two-component systems comprising an xcex1,xcex2-ethylenically unsaturated carbonyl compound and a polymer which contains activated CH2 groups, it being possible for the activated CH2 groups to be present either in the main chain or in the side chain or in both, as is described, for example, in EP-B-0 161 697 for (poly)malonate groups. Other compounds having activated CH2 groups are (poly)acetoacetates and (poly)cyanoacetates.
Two-component systems comprising an xcex1,xcex2-ethylenically unsaturated carbonyl compound and a (poly)malonate, and their preparation, are described in EP-B-0 161 687. The malonate group here can be attached in a polyurethane, polyester, polyacrylate, epoxy resin, polyamide or polyvinyl polymer either in the main chain or in a side chain. The xcex1,xcex2-ethylenically unsaturated carbonyl compound employed can be any double bond activated by a carbonyl group. Examples are esters or amides of acrylic acid or methacrylic acid. In the ester groups it is also possible for additional hydroxyl groups to be present. Diesters and triesters are also possible.
Typical examples are hexanediol diacrylate or trimethylolpropane triacrylate. Instead of the acrylic acid it is also possible to use other acids and their esters or amides, such as crotonic or cinnamic acid.
Under base catalysis, the components of the system react with one another at room temperature to form a crosslinked coating system which is suitable for numerous applications. Owing to its good inherent weathering resistance it is suitable, for example, for exterior applications as well and can, if required, be additionally stabilized by UV absorbers and other light stabilizers.
Other systems suitable as component B) in the novel compositions are epoxy systems. Epoxy resins are suitable for preparing novel, curable mixtures comprising epoxy resins as component B) are those which are customary in epoxy resin technology, examples of such epoxy resins being:
I) Polyglycidyl and poly(xcex2-methylglycidyl)esters, obtainable by reacting a compound, having at least two carboxyl groups in the molecule with epichlorohydrin or xcex2-methylepichlorohydrin. The reaction is judiciously carried out in the presence of bases. As the compound having at least two carboxyl groups in the molecule it is possible to use aliphatic polycarboxylic acids. Examples of such polycarboxylic acids are oxalic, succinic, glutaric, adipic, pimelic, suberic, azelaic or dimerized or trimerized linoleic acid. It is also possible, however, to employ cycloaliphatic polycarboxylic acids, such as tetrahydrophthalic, 4-methyltetrahydrophthalic, hexahydrophthalic or 4-methylhexahydrophthalic acid, for example. Aromatic polycarboxylic acids, furthermore, can be used, such as phthalic, isophthalic or terephthalic acid, for example.
II) Polyglycidyl or poly(xcex2-methylglycidyl) ethers, obtainable by reacting a compound having at least two free alcoholic hydroxyl groups and/or phenolic hydroxyl groups with epichlorohydrin or xcex2-methylepichlorohydrin under alkaline conditions or in the presence of an acidic catalyst with subsequent alkali treatment.
The glycidyl ethers of this type are derived, for example, from acyclic alcohols, such as ethylene glycol, diethylene glycol and higher poly(oxyethylene) glycols, propane-1,2-diol or poly(oxypropylene)glycols, propane-1,3-diol, butane-1,4-diol, poly(oxytetramethylene)glycols, pentane-1,5-diol, hexane-1,6-diol, hexane-2,4,6-triol, glycerol, 1,1,1-trimethylolpropane, pentaerythritol, sorbitol, and from polyepichlorohydrins. They also derive, however, for example, from cycloaliphatic alcohols, such as 1,4-cyclohexanedimethanol, bis(4-hydroxycyclohexyl)methane or 2,2-bis(4-hydroxycyclohexyl)propane, or possess aromatic nuclei, such as N,N-bis(2-hydroxyethyl)aniline or p,pxe2x80x2-bis(2-hydroxyethylamino)diphenylmethane. The glycidyl ethers can also be derived from mononuclear phenols, such as resorcinol or hydroquinone, for example, or are based on polynuclear phenols, such as bis(4-hydroxyphenyl)methane, 4,4xe2x80x2-dihydroxybiphenyl, bis(4-hydroxyphenyl)sulfone, 1,1,2,2-tetrakis(4-hydroxyphenyl)ethane, 2,2-bis(4-hydroxyphenyl)propane, 2,2-bis(3,5-dibromo-4-hydroxyphenyl)propane and from novolaks, obtainable by condensing aldehydes, such as formaldehyde, acetaldehyde, chloral or furfuraldehyde, with phenols, such as phenol, or with phenols whose nucleus is substituted by chlorine atoms or C1-C9alkyl groups, examples being 4-chlorophenol, 2-methylphenol, or 4-tert-butylphenol, or by condensation with bisphenols, those of the type specified above.
III) Poly(N-glycidyl) compounds, obtainable by dehydrochlorination of the reaction products of epichlorohydrin with amines containing at least two amine hydrogen atoms. These amines are, for example, aniline, n-butylamine, bis(4-aminophenyl)methane, m-xylylenediamine or bis(4-methylaminophenyl)methane.
The poly(N-glycidyl) compounds also, however, include triglycidyl isocyanurate, N,Nxe2x80x2-diglycidyl derivatives of cycloalkyleneureas, such as ethyleneurea or 1,3-propyleneurea, and diglycidyl derivatives of hydantoins, such as of 5,5-dimethylhydantoin.
IV) Poly(S-glycidyl) compounds, for example di-S-glycidyl derivatives derived from dithiols such as ethane-1,2-dithiol or bis(4-mercaptomethylphenyl) ether.
V) Cycloaliphatic epoxy resins, for example bis(2,3-epoxycyclopentyl) ether, 2,3-epoxycyclopentyl glycidyl ether, 1,2-bis(2,3-epoxycyclopentyloxy)ethane or 3,4-epoxycyclohexylmethyl3xe2x80x2,4xe2x80x2-epoxycyclohexanecarboxylate.
Alternatively it is possible to use epoxy resins in which the 1,2-epoxide groups are attached to different heteroatoms and/or functional groups; these compounds include, for example, the N,N,O-triglycidyl derivative of 4-aminophenol, the glycidyl ether glycidyl ester of salicylic acid, N-glycidyl-Nxe2x80x2-(2-glycidyloxypropyl)-5,5-dimethylhydantoin or 2-glycidyloxy-1,3-bis(5,5-dimethyl-1-glycidylhydantoin-3-yl)propane.
Mixtures of epoxy resins can also be used as component B).
The compositions comprise the photoinitiator, component A), preferably in an amount of from 0.01 to 10% by weight, based on the component B).
In addition to the photoinitiator, component A), the photopolymerizable mixtures may include various additives. Examples of these are thermal inhibitors which are intended to prevent premature polymerization, such as hydroquinone, hydroquinone derivatives, p-methoxyphenol, xcex2-naphthol or sterically hindered phenols such as 2,6-di(tert-butyl)-p-cresol, for example. To increase the dark storage stability it is possible, for example, to use copper compounds, such as copper naphthenate, stearate or octoate, phosphorus compounds, such as triphenylphosphine, tributylphosphine, triethyl phosphite, triphenyl phosphite or tribenzyl phosphite, quaternary ammonium compounds, such as tetramethylammonium chloride or trimethylbenzylammonium chloride, or hydroxylamine derivatives, such as N-diethyl-hydroxylamine. To exclude atmospheric oxygen during polymerization it is possible to add paraffin or similar waxlike substances, which owing to their lack of solubility in the polymer migrate to the surface at the beginning of polymerization where they form a transparent surface layer which prevents the ingress of air. It is likewise possible to apply an oxygen-impermeable layer. Light stabilizers which can be added, in a small amount, are UV absorbers such as those, for example, of the hydroxyphenylbenzotriazole, hydroxyphenyl-benzophenone, oxalamide or hydroxyphenyl-s-triazine type. Individual compounds or mixtures of these compounds can be used, with or without the deployment of sterically hindered amines (HALS).
Examples of such UV absorbers and light stabilizers are given below.
1. 2-(2xe2x80x2-Hydroxyphenyl)benzotriazoles, for example 2-(2xe2x80x2-hydroxy-5xe2x80x2-methylphenyl)benzotriazole, 2-(3xe2x80x2,5xe2x80x2-di-tert-butyl-2xe2x80x2-hydroxyphenyl)benzotriazole, 2-(5xe2x80x2-tert-butyl-2xe2x80x2-hydroxyphenyl)benzotriazole, 2-(2xe2x80x2-hydroxy-5xe2x80x2-(1,1,3,3-tetramethylbutyl)phenyl)benzotriazole, 2-(3xe2x80x2,5xe2x80x2-di-tert-butyl-2xe2x80x2-hydroxyphenyl)-5-chlorobenzotriazole, 2-(3xe2x80x2-tert-butyl-2xe2x80x2-hydroxy-5xe2x80x2-methylphenyl)-5-chlorobenzotriazole, 2-(3xe2x80x2-sec-butyl-5xe2x80x2-tert-butyl-2xe2x80x2-hydroxyphenyl)benzotriazole, 2-(2xe2x80x2-hydroxy-4xe2x80x2-octoxyphenyl)benzotriazole, 2-(3xe2x80x2,5xe2x80x2-di-tert-amyl-2xe2x80x2-hydroxyphenyl)benzotriazole, 2-(3xe2x80x2,5xe2x80x2-bis(xcex1,xcex1-dimethylbenzyl)-2xe2x80x2-hydroxyphenyl)benzotriazole, mixture of 2-(3xe2x80x2-tert-butyl-2xe2x80x2-hydroxy-5xe2x80x2-(2-octyloxycarbonylethyl)phenyl)-5-chlorobenzotriazole, 2-(3xe2x80x2-tert-butyl-5xe2x80x2-[2-(2-ethylhexyloxy)carbonylethyl]-2xe2x80x2-hydroxyphenyl)-5-chlorobenzotriazole, 2-(3xe2x80x2-tert-butyl-2xe2x80x2-hydroxy-5xe2x80x2-(2-methoxycarbonylethyl)phenyl)-5-chlorobenzotriazole, 2-(3xe2x80x2-tert-butyl-2xe2x80x2-hydroxy-5xe2x80x2-(2-methoxycarbonylethyl)phenyl)benzotriazole, 2-(3xe2x80x2-tert-butyl-2xe2x80x2-hydroxy-5xe2x80x2-(2-octyloxycarbonylethyl)phenyl)benzotriazole, 2-(3xe2x80x2-tert-butyl-5xe2x80x2-[2-(2-ethylhexyloxy)carbonylethyl]-2xe2x80x2-hydroxyphenyl)benzotriazole, 2-(3xe2x80x2-dodecyl-2xe2x80x2-hydroxy-5xe2x80x2-methylphenyl)benzotriazole and 2-(3xe2x80x2-tert-butyl-2xe2x80x2-hydroxy5xe2x80x2-(2-isooctyloxycarbonylethyl)phenylbenzotriazole, 2,2xe2x80x2-methylenebis[4-(1,1,3,3-tetra-methylbutyl)-6-benzotriazol-2-ylphenol]; transesterification product of 2-[3xe2x80x2-tert-butyl-5xe2x80x2-(2-methoxycarbonylethyl)-2xe2x80x2-hydroxyphenyl]benzotriazole with polyethylene glycol 300; [Rxe2x80x94CH2CH2xe2x80x94COO(CH2)3]2xe2x80x94 where R=3xe2x80x2-tert-butyl-4xe2x80x2-hydroxy-5xe2x80x2-2H-benzotriazol-2-ylphenyl.
2. 2-Hydroxybenzophenones, for example the 4-hydroxy, 4-methoxy-, 4-octoxy-, 4-decyloxy, 4-dodecyloxy, 4-benzyloxy, 4,2xe2x80x2,4xe2x80x2-trihydroxy and 2xe2x80x2-hydroxy-4,4xe2x80x2-dimethoxy derivative.
3. Esters of substituted and unsubstituted benzoic acids, for example 4-tert-butylphenyl salicylate, phenyl salicylate, octylphenyl salicylate, dibenzoylresorcinol, bis(4-tert-butylbenzoyl)resorcinol, benzoylresorcinol, 2,4-di-tert-butylphenyl 3,5-di-tert-butyl-4-hydroxybenzoate, hexadecyl 3,5-di-tert-butyl-4-hydroxybenzoate, octadecyl 3,5-di-tert-butyl-4-hydroxybenzoate and 2-methyl-4,6-di-tert-butylphenyl 3,5-di-tert-butyl-4-hydroxybenzoate.
4. Acrylates, for example ethyl or isooctyl xcex1-cyano-xcex2,xcex2-diphenylacrylate, methyl xcex1-carbomethoxycinnamate, methyl and butyl xcex1-cyano-xcex2-methyl-p-methoxycinnamate, methyl xcex1-carbomethoxy-p-methoxycinnamate and N-(xcex2-carbomethoxy-xcex2-cyanovinyl)-2-methylindoline.
5. Sterically hindered amines, such as bis(2,2,6,6-tetramethylpiperidyl)sebacate, bis(2,2,6,6-tetramethylpiperidyl)succinate, bis(1,2,2,6,6-pentamethylpiperidyl)sebacate, bis(1,2,2,6,6-pentamethylpiperidyl)n-butyl-3,5-di-tert-butyl-4-hydroxybenzylmalonate, condensation product of 1-hydroxyethyl-2,2,6,6-tetramethyl-4-hydroxypiperidine and succinic acid, condensation product of N,Nxe2x80x2-bis(2,2,6,6-tetramethyl-4-piperidyl)hexamethylenediamine and 4-tert-octylamino-2,6-dichloro-1,3,5-s-triazine, tris(2,2,6,6-tetramethyl-4-piperidyl)nitrilotriacetate, tetrakis(2,2,6,6-tetramethyl-4-piperidyl)-1,2,3,4-butanetetraoate, 1,1xe2x80x2-(1,2-ethanediyl)-bis(3,3,5,5-tetramethylpiperazinone), 4-benzoyl-2,2,6,6-tetramethylpiperidine, 4-stearyloxy-2,2,6,6-tetramethylpiperidine, bis(1,2,2,6,6-pentamethylpiperidyl)2-n-butyl-2-(2-hydroxy-3,5-di-tert-butylbenzyl)malonate, 3-n-octyl-7,7,9,9-tetramethyl-1,3,8-triazaspiro[4.5]decane-2,4-dione, bis(1-octyloxy-2,2,6,6-tetramethylpiperidyl)sebacate, bis(1-octyloxy-2,2,6,6-tetramethylpiperidyl)succinate, condensation product of N,Nxe2x80x2-bis(2,2,6,6-tetramethyl-4-piperidyl)hexamethylenediamine and 4-morpholino-2,6-dichloro-1,3,5-triazine, condensation product of 2-chloro-4,6-di-(4-n-butylamino-2,2,6,6-tetramethylpiperidyl)-1,3,5-triazine and 1,2-bis(3-aminopropylamino)ethane, condensation product of 2-chloro-4,6-di-(4-n-butylamino-1,2,2,6,6-pentamethylpiperidyl)-1,3,5-triazine and 1,2-bis(3-aminopropylamino)ethane, 8-acetyl-3-dodecyl-7,7,9,9-tetramethyl-1,3,8-triazaspiro[4.5]decane-2,4-dione, 3-dodecyl-1-(2,2,6,6-tetramethyl-4-piperidyl)pyrrolidine-2,5-dione, 3-dodecyl-1-(1,2,2,6,6-pentamethyl-4-piperidyl)pyrrolidine-2,5-dione.
6. Oxalamides, for example 4,4xe2x80x2-dioctyloxyoxanilide, 2,2xe2x80x2-diethoxyoxanilide, 2,2xe2x80x2-dioctyloxy-5,5xe2x80x2-di-tert-butyloxanilide, 2,2xe2x80x2-di-dodecyloxy-5,5xe2x80x2di-tert-butyloxanilide, 2-ethoxy-2xe2x80x2-ethyloxanilide, N,Nxe2x80x2-bis(3-dimethylaminopropyl)oxalamide, 2-ethoxy-5-tert-butyl-2xe2x80x2-ethyloxanilide and its mixture with 2-ethoxy-2xe2x80x2-ethyl-5,4xe2x80x2-di-tert-butyloxanilide, mixtures of o- and p-methoxy- and of o- and p-ethoxy-disubstituted oxanilides.
7. 2-(2-Hydroxyphenyl)-1,3,5-triazines, for example 2,4,6-tris(2-hydroxy-4-octyloxyphenyl)-1,3,5-triazine, 2-(2-hydroxy-4-octyloxyphenyl)-4,6-bis(2,4-dimethylphenyl)-1,3,5-triazine, 2-(2,4-dihydroxyphenyl)-4,6-bis(2,4-dimethylphenyl)-1,3,5-triazine, 2,4-bis(2-hydroxy-4-propyloxyphenyl)-6-(2,4-dimethylphenyl)-1,3,5-triazine, 2-(2-hydroxy-4-octyloxyphenyl)-4,6-bis(4-methylphenyl)-1,3,5-triazine, 2-(2-hydroxy-4-dodecyloxyphenyl)-4,6-bis(2,4dimethylphenyl)-1,3,5-triazine, 2-[2-hydroxy-4-(2-hydroxy-3-butyloxypropyloxy)phenyl]-4,6bis(2,4-dimethylphenyl)-1,3,5-triazine, 2-[2-hydroxy-4-(2-hydroxy -3-octyloxy-propyloxy)phenyl]-4,6-bis(2,4-dimethylphenyl)-1,3,5-triazine, 2-[4-dodecyl/tridecyloxy-(2-hydroxypropyl)oxy-2-hydroxyphenyl]-4,6-bis(2,4-dimethylphenyl)-1,3,5-triazine.
8. Phosphites and phosphonites, for example, triphenyl phosphite, diphenyl alkyl phosphites, phenyl dialkyl phosphites, tris(nonylphenyl)phosphite, trilauryl phosphite, trioctadecyl phosphite, distearyl pentaerythritol diphosphite, tris(2,4-di-tert-butylphenyl)phosphite, diisodecyl pentaerythritol diphosphite, bis(2,4-di-tert-butylphenyl)pentaerythritol diphosphite, bis(2,6-di-tert-butyl-4-methylphenyl)pentaerythritol diphosphite, bis-isodecyloxy pentaerythritol diphosphite, bis(2,4-di-tert-butyl-6-methylphenyl)pentaerythritol diphosphite, bis(2,4,6-tri-tert-butylphenyl)pentaerythritol diphosphite, tristearyl sorbitol triphosphite, tetrakis(2,4-di-tert-butylphenyl)-4,4xe2x80x2-biphenylenediphosphonite, 6-isooctyloxy-2,4,8,10-tetra-tert-butyl-12H-dibenzo[d,g]-1,3,2-dioxaphosphocin, 6-fluoro-2,4,8,10-tetra-tert-butyl-12-methyldibenzo[d,g]-1,3,2-dioxaphosphocin, bis-(2,4-di-tert-butyl-6-methylphenyl)methyl phosphite, bis(2,4-di-tert-butyl-6-methylphenyl)ethyl phosphite.
Examples of further additives are:
Fillers and reinforcing agents, for example calcium carbonate, silicates, glass fibres, glass beads, asbestos, talc, kaolin, mica, barium sulfate, metal oxides and hydroxides, carbon black, graphite, wood flour and flours or fibres of other natural products, synthetic fibres.
Other additives, for example plasticizers, lubricants, emulsifiers, pigments, rheological additives, catalysts, levelling assistants, optical brighteners, flameproofing agents, antistatics, blowing agents.
In addition to the additives indicated above it is also possible for additional coinitiators to be present. In general these are dyes which improve the overall quantum yield by means, for example, of energy transfer or electron transfer. Examples of suitable dyes which can be added as coinitiators are triarylmethanes, for example malachite green, indolines, thiazines, for example methylene blue, xanthones, thioxanthones, oxazines, acridines or phenazines, for example safranine, and rhodamines of the formula 
in which R is alkyl or aryl and Rxe2x80x2 is hydrogen, an alkyl or aryl radical, for example Rhodamine B, Rhodamine 6G or Violamine R, and also Sulforhodamine B or Sulforhodamine G.
Preference is given to thioxanthones, oxazines, acridines, phenazines and rhodamines.
In addition to the above-described base-catalysable (curable) binders, component B), the composition may also include other binders as well. Further olefinically unsaturated compounds, for example, are possible. The unsaturated compounds may include one or more olefinically double bonds. They may be of low molecular mass (monomeric) or higher molecular mass (oligomeric). Examples of monomers having a double bond are alkyl or hydroxyalkyl acrylates or methacrylates, such as methyl, ethyl, butyl, 2-ethylhexyl or 2-hydroxyethyl acrylate, isbornyl acrylate, methyl methacrylate or ethyl methacrylate. Silicone acrylates are also of interest. Further examples are acrylonitrile, acrylamide, methacrylamide, N-substituted (meth)acrylamides, vinyl esters such as vinyl acetate, vinyl ethers such as isobutyl vinyl ether, styrene, alkyl- and halostyrenes, N-vinylpyrrolidone, vinyl chloride or vinylidene chloride.
Examples of monomers having two or more double bonds are the diacrylates of ethylene glycol, propylene glycol, neopentyl glycol, hexamethylene glycol or bisphenol A, 4,4xe2x80x2-bis(2-acryloyloxyethoxy)diphenylpropane, trimethylolpropane triacrylate, pentaerythritol triacrylate or tetraacrylate, vinyl acrylate, divinyl benzene, divinyl succinate, diallyl phthalate, triallyl phosphate, triallyl isocyanurate or tris(2-acryloylethyl)isocyanurate.
Examples of polyunsaturated compounds of relatively high molecular mass (oligomers) are acrylicized epoxy resins, acrylicized polyesters or polyesters containing vinyl ether groups or epoxy groups, polyurethanes and polyethers. Further examples of unsaturated oligomers are unsaturated polyester resins which are mostly prepared from maleic acid, phthalic acid and one or more diols and have molecular weights of from about 500 to 3000. In addition it is also possible to employ vinyl ether monomers and oligomers, and also maleate-terminated oligomers with polyester, polyurethane, polyether, polyvinyl ether and epoxy main chains. In particular, combinations of vinyl ether-functional oligomers and polymers as are described in WO 90/01512 are very suitable. Also suitable, however, are copolymers of vinyl ether and maleic acid-functionalized monomers. Unsaturated oligomers of this kind can also be referred to as prepolymers.
Particularly suitable examples are esters of ethylenically unsaturated carboxylic acids and polyols or polyepoxides, and polymers having ethylenically unsaturated groups in the chain or in side groups, such as unsaturated polyesters, polyamides and polyurethanes and copolymers thereof, alkyd resins, polybutadiene and butadiene copolymers, polyisoprene and isoprene copolymers, polymers and copolymers having (meth)acrylic groups in side chains, and mixtures of one or more such polymers.
If, in addition, use is made of such free-radically curable monomers, oligomers/polymers then it is judicious to add a further photoinitiator which dissociates into free radicals. Such photoinitiators are known and are produced industrially. Examples are benzophenone, benzophenone derivatives, acetophenone, acetophenone derivatives, for example xcex1-hydroxycycloalkyl phenyl ketones, dialkoxyacetophenones, xcex1-hydroxy- or xcex1-aminoacetophenones, 4-aroyl-1,3-dioxolanes, benzoin alkyl ethers and benzil ketals, monoacyl phosphine oxides, bisacylphosphine oxides, ferrocenium compounds or titanocenes. Examples are specified in U.S. Pat. No. 5,077,402. Polymer systems of this kind, in which curing/crosslinking takes place by different mechanisms, are also referred to as hybrid systems.
The novel compositions can also have added to them non-reactive binders, which is particularly judicious if the photopolymerizable compounds are liquid or viscous substances. The amount of the non-reactive binder can be, for example, 5-95%, preferably 10-90% and, in particular, 40-90% by weight, based on the overall solids content. The choice of non-reactive binder is made in accordance with the field of use and with the properties required for this use, such as the possibility for development in aqueous and organic solvent systems, adhesion to substrates, and sensitivity to oxygen.
Examples of suitable binders are polymers having a molecular weight of around 5000-2,000,000, preferably 10,000-1,000,000. Examples are: homo- and copolymeric acrylates and methacrylates, for example copolymers of methyl methacrylate/ethyl acrylate/methacrylic acid, poly(alkyl methacrylates), poly(alkyl acrylates); cellulose esters and ethers, such as cellulose acetate, cellulose acetate butyrate, methylcellulose, ethylcellulose; polyvinylbutyral, polyvinylformal, cyclized rubber, polyethers such as polyethylene oxide, polypropylene oxide, polytetrahydrofuran; polystyrene, polycarbonate, polyurethane, chlorinated polyolefins, polyvinyl chloride, copolymers of vinyl chloride/vinylidene chloride, copolymers of vinylidene chloride with acrylonitrile, methyl methacrylate and vinyl acetate, polyvinyl acetate, copoly(ethylene/vinyl acetate), polymers such as polycaprolactam and poly(hexamethylene adipamide) and polyesters such as poly(ethylene glycol terephtalate) and poly(hexamethylene glycol succinate).
The invention additionally provides a method of implementing base-catalysed reactions which comprises subjecting
A) at least one compound comprising a structural unit of the formula (I) 
in which R1 is an aromatic or heteroaromatic radical which is capable of absorbing light in the wavelength range from 200 to 650 nm and in doing so brings about cleavage of the adjacent carbon-nitrogen bond; and
B) at least one organic compound which is capable of a base-catalysed reaction to irradiation with light having a wavelength of from 200 nm to 650 nm.
Component A) is preferably an organic compound in which the structural unit of the formula (I) comprises compounds of the formula (II) 
in which R1, R2, R3, R4, R5, R6 and R7 are as defined above, including their preferred meanings.
Examples and preferred meanings for base-catalysed reactions have already been given above.
With particular preference, component B) is an anionically polymerizable or crosslinkable organic material.
In some cases it may be advantageous to carry out heating during or after exposure to light. In this way it is possible in many cases to accelerate the crosslinking reaction.
The sensitivity of the novel compositions to light generally extends from about 200 nm through the UV region and into the infrared region (about 20,000 nm, in particular 1200 nm) and therefore spans a very broad range. Suitable radiation comprises, for example, sunlight or light from artificial light sources. Therefore, a large number of very different types of light source can be used. Both point sources and flat radiators (lamp carpets) are suitable. Examples are carbon arc lamps, xenon arc lamps, medium-pressure, high-pressure and low-pressure mercury lamps, doped if desired with metal halides (metal halogen lamps), microwave-stimulated metal vapour lamps, excimer lamps, superactinic fluorescent tubes, fluorescent lamps, incandescent argon lamps, electronic flashlights, photographic flood lamps, electron beams and X-rays, produced by means of synchrotrons or laser plasma. The distance between the lamp and the substrate according to the invention which is to be exposed can vary depending on the application and on the type and/or power of the lamp, for example between 2 cm and 150 cm. Also especially suitable are laser light sources, for example excimer lasers. Lasers in the visible region or in the IR region can also be employed. Very advantageous here is the high sensitivity of the novel materials and the possibility of adapting a dye as coinitiator to the laser line. By this method it is possible to produce printed circuits in the electronics industry, lithographic offset printing plates or relief printing plates, and also photographic image recording materials.
The novel compositions can be employed for various purposes, for example as printing inks, as clearcoats, as white paints, for example for wood or metal, as coating materials, inter alia for paper, wood, metal or plastic, as powder coatings, as daylight-curable coatings for marking buildings and roads, for photographic reproduction processes, for holographic recording materials, for image recording processes or for the production of printing plates which can be developed using organic solvents or aqueous-alkaline media, for the production of masks for screen printing, as dental filling materials, as adhesives, including pressure-sensitive adhesives, as laminating resins, as etch resists or permanent resists and as solder masks for electronic circuits, for the production of three-dimensional articles by mass curing (UV curing in transparent moulds) or by the stereolithography process, as is described, for example, in U.S. Pat. No. 4,575,330, for the preparation of composite materials (for example styrenic polyesters, which may contain glass fibres and/or other fibres and other assistants) and other thick-layer compositions, for the coating or encapsulation of electronic components, or as coatings for optical fibres.
In surface coatings, it is common to use mixtures of a prepolymer with polyunsaturated monomers which also contain a monounsaturated monomer. The prepolymer here is primarily responsible for the properties of the coating film, and varying it allows the skilled worker to influence the properties of the cured film. The polyunsaturated monomer functions as a crosslinker, which renders the coating film insoluble. The monounsaturated monomer functions as a reactive diluent, by means of which the viscosity is reduced without the need to use a solvent.
Unsaturated polyester resins are mostly used in two-component systems in conjunction with a monounsaturated monomer, preferably styrene. For photoresists, specific one-component systems are frequently employed, for example polymaleinimides, polychalcones or polyimides, as described in DE-A-2 308 830.
The novel photocurable compositions are suitable, for example, as coating materials for substrates of all kinds, examples being wood, textiles, paper, ceramic, glass, plastics such as polyesters, polyethylene terephthalate, polyolefins or cellulose acetate, especially in the form of films, and also metals such as Al, Cu, Ni, Fe, Zn, Mg or Co and GaAs, Si or SiO2, on which it is the intention to apply a protective coating or, by imagewise exposure, an image.
The substrates can be coated by applying a liquid composition, a solution or suspension to the substrate. The choice of solvent and the concentration depend predominantly on the type of composition and the coating process. The solvent should be inert: in other words, it should not undergo any chemical reaction with the components and should be capable of being removed again after the coating operation, in the drying process. Examples of suitable solvents are ketones, ethers and esters, such as methyl ethyl ketone, isobutyl methyl ketone, cyclopentanone, cyclohexanone, N-methylpyrrolidone, dioxane, tetrahydrofuran, 2-methoxyethanol, 2-ethoxyethanol, 1-methoxy-2-propanol, 1,2-dimethoxyethane, ethyl acetate, n-butyl acetate and ethyl 3-ethoxypropionate.
Using known coating processes, the solution is applied uniformly to a substrate, for example by spin coating, dip coating, knife coating, curtain coating, brushing, sprayingxe2x80x94especially electrostatic sprayingxe2x80x94and reverse roll coating and by electrophoretic deposition. It is also possible to apply the photosensitive layer to a temporary, flexible support and then to coat the final substrate, for example a copper-clad circuit board, by means of layer transfer via lamination.
The amount applied (layer thickness) and the nature of the substrate (layer support) are functions of the desired field of application. The range of layer thicknesses generally comprises values from about 0.1 xcexcm to more than 100 xcexcm.
The novel radiation-sensitive compositions can also be subjected to imagewise exposure. In this case they are used as negative resists. They are suitable for electronics (galvanoresists, etch resists and solder resists), for the production of printing plates, such as offset printing plates, flexographic and relief printing plates or screen printing plates, for the production of marking stamps, and can be used for chemical milling or as micro resists in the production of integrated circuits. There is a correspondingly wide range of variation in the possible layer supports and in the processing conditions of the coated substrates.
The term xe2x80x9cimagewisexe2x80x9d exposure relates both to exposure through a photomask containing a predetermined pattern, for example a slide, exposure by a laser beam which is moved under computer control, for example, over the surface of the coated substrate and so generates an image, and irradiation with computer-controlled electron beams.
Following the imagewise exposure of the material and prior to developing, it may be advantageous to carry out a brief thermal treatment, in which only the exposed parts are thermally cured. The temperatures employed are generally 50-150xc2x0 C. and preferably 80-130xc2x0 C.; the duration of the thermal treatment is generally between 0.25 and 10 minutes.
A further field of use for photocuring is that of metal coating, for example the surface-coating of metal panels and tubes, cans or bottle tops, and photocuring on polymer coatings, for example of floor or wall coverings based on PVC.
Examples of the photocuring of paper coatings are the colourless varnishing of labels, record sleeves or book covers.
The use of the novel compounds for curing shaped articles made from composite compositions is likewise of interest. The composite composition is made up of a self-supporting matrix material, for example a glass-fibre fabric, or else, for example, of plant fibres [cf. K.-P. Mieck, T. Reussmann in Kunststoffe 85 (1995), 366-370], which is impregnated with the photocuring formulation. Shaped articles which are produced from composite compositions using the compounds according to the invention are of high mechanical stability and resistance. The compounds of the invention can also be used as photocuring agents in moulding, impregnating and coating compositions, as are described, for example, in EP-A-7086. Examples of such compositions are fine coating resins on which stringent requirements are placed with respect to their curing activity and resistance to yellowing, or fibre-reinforced mouldings such as planar or longitudinally or transversely corrugated light diffusing panels.
The invention additionally provides for the use of an organic compound comprising at least one structural unit of the formula (I) 
in which R1 is an aromatic or heteroaromatic radical which is capable of absorbing light in the wavelength range from 200 to 650 nm and on doing so brings about cleavage of the adjacent carbon-nitrogen bond, as a photoinitiator for photochemically induced, base-catalysed addition or substitution reactions.
Preference is given to an organic compound in which the structural unit of the formula (I) comprises compounds of the formula (II) 
in which the radicals R1, R2, R3, R4, R5, R6 and R7 are as defined above, including their preferred meanings.
Examples and preferences for base-catalysed addition or substitution reactions have been given above.
The invention provides, furthermore, a coated substrate which has been coated on at least one surface with a composition as described above, and a process for the photographic production of relief images, in which a coated substrate is subjected to imagewise exposure and then the unexposed areas are removed with a solvent. Of particular interest in this context is the abovementioned exposure by means of a laser beam.